Pola and Dr. Goldsteins' posts on JAK2 homozygous vs heterozygous (tomorrow at 1:00 PM)

[Memo To Me]

http://www.mpdsupport.org You recently provided links to a couple of interesting papers in the current issue of Blood (1 Aug 2007). However, the same issue contains a third article, a sort of editorial, by Prof. Prchal. Since it sums up the other two very nicely, I believe it will be of interest to the rest of the list members:

http://bloodjournal.hematologylibrary.org/cgi/content/full/110/3/796

Thanks for all the links to original papers that you give us! I probably wouldn't find half of them on my own. In this case, though, I subscribe to the table of contents of Blood, which is probably the most relevant single publication.

Anyone who is interested can get the table of contents of Blood and access the abstracts for free. The table of contents of the New England Journal of Medicine is also of interest, less for specific papers on MPDs than for articles on the situation of medicine in general.

Best regards, Pola
(*1940, PV dx 2002, JAK2+, occasional phlebs, ASA 50mg)

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Dick,

You are not alone. I have a medical degree and am still struggling to fully understand the meaning and significance of the emerging research findings regarding the JAK2 mutation.

The 2 recent articles in Blood that Robert referred me to were very helpful, though they still paint a very complex picture.

Here is my understanding..... Everyone has JAK2 genes. When a specific mutation occurs in the JAK2 gene folks get MPDs, particularly PV.. Research has determined that aJAK2 gene carries a mutation in over 90% of folks with PV. Both you and I are JAK2 positive, meaning we are among the 90% with the JAK2 mutation in our cells.

However, it turns out that having the JAK2 mutation is not an all or nothing event. There are 2 copies, called alleles, of each JAK2 gene. These cells can either have neither of the 2 alleles with the JAK2 mutation (these folks are JAK2 negative), 1 of the 2 alleles with the JAK2 mutation (called heterozygous) or both of the alleles with the JAK2 mutation (called homozygous).

Complicating matters, a person can have some cells that are homozygous for the JAK2 mutation, some cells that are heterozygous and some cells that have the normal JAK2 gene. The test that looks for the JAK2 mutation generally uses white blood cells taken from your blood. The qualitative test that was the only test done until recently reported the result as positive when any of the alleles had the JAK2 mutation. Now, researchers can actually measure the percentage of alleles that carry the mutation, called a quantitative JAK2 mutation test. When more than 50% of the alleles tested carry the JAK2 mutation, one can assume that at least some of the cells are homozygous for the mutation. A result like mine, 48% is more equivocal, as some of my cells may be homozygous and some heterozygous, averaging out to 48% positive.

Why is this important? Well, as you might expect, recent research, reported only this month, has suggested that being homozygous for the JAK2 mutation is associated with more severe disease and poorer ou

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